I recently tried to setup sendgrid to send emails but I realized I don't even have any email account on those domains.
What would you say is the best/cheapest way to buy an email-enabled domain?
Thanks.
You just have to setup an email server (or buy 'email server' access from someone who sells the same) somewhere that handles email for the domains. And then point the MX records in DNS for the domains for which you want to receive email at the email servers that handle email for those domains.
Since you're already with Namecheap, why not go with one of their email plans/addons?
All you have to do is add an MX record in the DNS and you've email-ified the domain.
I own a domain handled by NameCheap on which I send and receive email. Originally I were running my own email servers, but I quickly realised that was more work than it was worth in my case, so now email sent and received on my NameCheap domain gets handled by FastMail.
...but yes, it would be nice if someone offered a non-price-gouge-y option for all the things you'd need to get dangerous.